1. Field of the Invention
The present invention relates generally to the field of poured or cast concrete construction, and, more specifically, to an attachment system for strongback beams on concrete panels to reinforce the panel against fracture or damage during a tilt-up operation.
2. Description of Related Art
One technique for erecting concrete structures involves the formation of concrete slabs or panels, generally at the construction site, and thereafter tilting such panels up into place. Oftentimes, openings are required in the concrete panels which will normally create extreme bending stresses in the remaining concrete sections. Although internal reinforcing steel may be utilized, one common way to counter such bending stresses and increase the stiffness of the panel is the use of strongback beams, or "strongbacks," which are attached temporarily to the concrete panel.
Strongbacks are an efficient and economical method and generally involve the use of wood or steel beams being attached at critical locations. One manner of attaching strongbacks to a concrete panel is described in the Dayton Superior Corporation's tilt-up construction handbook and involves a strongback bolt being threadably engaged with a strongback insert positioned within the concrete panel. However, it has been found that this method of attachment is somewhat time-consuming and an attachment method which would allow quick and simple connection and release would be desirable.
In this regard, a strongback attachment system described in U.S. Pat. No. 5,212,920, to Richmond Screw Anchor Company, describes a system which is quickly installed. As seen therein, the '920 patent discloses a strongback attachment system which includes a bolt-type assembly, an insert, and a strongback beam. The insert, which is in the form of a support chair, includes a substantially U-shaped member which may be engaged by one end of the bolt assembly. More specifically, the engagement head of the bolt assembly has a slot formed therein which is sized to receive the U-shaped member. Thereafter, a pair of hook elements adjacent to the slot engage the U-shaped member by a twist of the bolt assembly and a spring loaded pin retains it in engagement with the hook elements.
Although the strongback attachment system described in U.S. Pat. No. 5,212,920 is able to perform its intended function, it has been found that the engagement head utilized therein is relatively complicated and expensive to produce. Moreover, alignment of the bolt assembly engagement head with the U-shaped member of the insert provides very little in the way of tolerance. Therefore, it would be desirable for a strongback attachment system to be developed which not only is able to be connected and disconnected quickly, but one which is simpler and more economical in design.
Accordingly, one object of the present invention is to provide a strongback attachment system which allows a strongback beam to be connected and disconnected quickly and simply.
Another object of the present invention is to provide a strongback attachment system which is self contained.
Yet a further object of the present invention is to provide a strongback attachment system which has a simple and economic design.
Still a further object of the present invention is to provide a strongback attachment system which provides a more stable connection to the insert embedded in the concrete panel.